/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.socket.client.jetty;

import java.net.URI;
import java.security.Principal;
import java.util.List;
import java.util.Map;
import java.util.concurrent.Callable;
import java.util.concurrent.Future;

import org.eclipse.jetty.websocket.api.Session;
import org.eclipse.jetty.websocket.client.ClientUpgradeRequest;
import org.eclipse.jetty.websocket.client.WebSocketClient;

import org.springframework.context.Lifecycle;
import org.springframework.core.task.AsyncListenableTaskExecutor;
import org.springframework.core.task.SimpleAsyncTaskExecutor;
import org.springframework.core.task.TaskExecutor;
import org.springframework.http.HttpHeaders;
import org.springframework.lang.Nullable;
import org.springframework.util.concurrent.ListenableFuture;
import org.springframework.util.concurrent.ListenableFutureTask;
import org.springframework.web.socket.WebSocketExtension;
import org.springframework.web.socket.WebSocketHandler;
import org.springframework.web.socket.WebSocketSession;
import org.springframework.web.socket.adapter.jetty.JettyWebSocketHandlerAdapter;
import org.springframework.web.socket.adapter.jetty.JettyWebSocketSession;
import org.springframework.web.socket.adapter.jetty.WebSocketToJettyExtensionConfigAdapter;
import org.springframework.web.socket.client.AbstractWebSocketClient;
import org.springframework.web.util.UriComponents;
import org.springframework.web.util.UriComponentsBuilder;

/**
 * Initiates WebSocket requests to a WebSocket server programmatically
 * through the Jetty WebSocket API.
 *
 * <p>As of 4.1 this class implements {@link Lifecycle} rather than
 * {@link org.springframework.context.SmartLifecycle}. Use
 * {@link org.springframework.web.socket.client.WebSocketConnectionManager
 * WebSocketConnectionManager} instead to auto-start a WebSocket connection.
 *
 *
 * jetty webSocket 客户端
 * @author Rossen Stoyanchev
 * @since 4.0
 */
public class JettyWebSocketClient extends AbstractWebSocketClient implements Lifecycle {

    // 客户端
    private final org.eclipse.jetty.websocket.client.WebSocketClient client;

    @Nullable
    private AsyncListenableTaskExecutor taskExecutor = new SimpleAsyncTaskExecutor();


    /**
     * Default constructor that creates an instance of
     * {@link org.eclipse.jetty.websocket.client.WebSocketClient}.
     */
    public JettyWebSocketClient() {
        this.client = new org.eclipse.jetty.websocket.client.WebSocketClient();
    }

    /**
     * Constructor that accepts an existing
     * {@link org.eclipse.jetty.websocket.client.WebSocketClient} instance.
     */
    public JettyWebSocketClient(WebSocketClient client) {
        this.client = client;
    }

    /**
     * Return the configured {@link TaskExecutor}.
     */
    @Nullable
    public AsyncListenableTaskExecutor getTaskExecutor() {
        return this.taskExecutor;
    }

    /**
     * Set an {@link AsyncListenableTaskExecutor} to use when opening connections.
     * If this property is set to {@code null}, calls to any of the
     * {@code doHandshake} methods will block until the connection is established.
     * <p>By default an instance of {@code SimpleAsyncTaskExecutor} is used.
     */
    public void setTaskExecutor(@Nullable AsyncListenableTaskExecutor taskExecutor) {
        this.taskExecutor = taskExecutor;
    }

    @Override
    public void start() {
        try {
            // 开始
            this.client.start();
        }
        catch (Exception ex) {
            throw new IllegalStateException("Failed to start Jetty WebSocketClient", ex);
        }
    }

    @Override
    public void stop() {
        try {
            // 关闭
            this.client.stop();
        }
        catch (Exception ex) {
            logger.error("Failed to stop Jetty WebSocketClient", ex);
        }
    }

    @Override
    public boolean isRunning() {
        // 是否属于运行状态
        return this.client.isStarted();
    }


    @Override
    public ListenableFuture<WebSocketSession> doHandshake(WebSocketHandler webSocketHandler,
                                                          String uriTemplate, Object... uriVars) {

        UriComponents uriComponents = UriComponentsBuilder.fromUriString(uriTemplate).buildAndExpand(uriVars).encode();
        return doHandshake(webSocketHandler, null, uriComponents.toUri());
    }

    @Override
    public ListenableFuture<WebSocketSession> doHandshakeInternal(WebSocketHandler wsHandler,
                                                                  HttpHeaders headers, final URI uri, List<String> protocols,
                                                                  List<WebSocketExtension> extensions, Map<String, Object> attributes) {

        final ClientUpgradeRequest request = new ClientUpgradeRequest();
        request.setSubProtocols(protocols);

        for (WebSocketExtension e : extensions) {
            request.addExtensions(new WebSocketToJettyExtensionConfigAdapter(e));
        }

        headers.forEach(request::setHeader);

        Principal user = getUser();
        final JettyWebSocketSession wsSession = new JettyWebSocketSession(attributes, user);
        final JettyWebSocketHandlerAdapter listener = new JettyWebSocketHandlerAdapter(wsHandler, wsSession);

        Callable<WebSocketSession> connectTask = () -> {
            Future<Session> future = this.client.connect(listener, uri, request);
            future.get();
            return wsSession;
        };

        if (this.taskExecutor != null) {
            return this.taskExecutor.submitListenable(connectTask);
        }
        else {
            ListenableFutureTask<WebSocketSession> task = new ListenableFutureTask<>(connectTask);
            task.run();
            return task;
        }
    }

    /**
     * Return the user to make available through {@link WebSocketSession#getPrincipal()}.
     * By default this method returns {@code null}
     */
    @Nullable
    protected Principal getUser() {
        return null;
    }

}
